Implement the ic-height metric of font-size-adjust

This CL adds the ic-height metric support to font-size-adjust [1]. The
ic-height metric lets developers adjust font size relative to the height
of the CJK water glyph. A note-worthy is the fallback case where the
used font does not provide vertical font info. Such vertical font info
is often missing, but the current specification does not describe the
fallback behavior. As a temporary measure, we use the advance width of
the CJK water glyph instead until the standard fallback behavior is
established [2] if we cannot get its advance height from the font. That
would be a sensible approximation since the CJK water glyph has the same
width and height in most fonts.

[1] https://www.w3.org/TR/css-fonts-5/#valdef-font-size-adjust-ic-height
[2] w3c/csswg-drafts#8792

Test:
external/wpt/css/css-fonts/animations/font-size-adjust-composition.html
external/wpt/css/css-fonts/font-size-adjust-ic-height.html (new)
external/wpt/css/css-fonts/parsing/font-size-adjust-computed.html
external/wpt/css/css-fonts/parsing/font-size-adjust-valid.html

Bug: 1219875
Change-Id: Ie90a6241cb7e8a55fcaf65df5a4edc1058028ebe

Author: shivamidow

css/css-fonts/font-size-adjust-ic-height-ref.html

@@ -0,0 +1,25 @@
+>
+<meta charset="UTF-8">
+<title>font-size-adjust with the ic-height metrictitle>
+<link rel="author" title="ChangSeok Oh" href="mailto:[email protected]" />
+<style>
+@font-face {
+  font-family: NotoSansCJK;
+  src: url(/fonts/noto/cjk/NotoSansCJKjp-Regular-subset-chws.otf);
+}
+div {
+  font-family: NotoSansCJK;
+  color: green;
+  background: green;
+  writing-mode: vertical-rl;
+  text-orientation: upright;
+}
+.valueRef {
+  font-size: 200px;
+}
+.fromFontRef {
+  font-size: 100px;
+}
+style>
+<div class="valueRef">水div>
+<div class="fromFontRef">水div>

css/css-fonts/font-size-adjust-ic-height.html

@@ -0,0 +1,33 @@
+>
+<meta charset="UTF-8">
+<title>font-size-adjust with the ic-height metrictitle>
+<link rel="author" title="ChangSeok Oh" href="mailto:[email protected]" />
+<link rel="help" href="https://www.w3.org/TR/css-fonts-5/#valdef-font-size-adjust-ic-height" />
+<link rel="match" href="font-size-adjust-ic-height-ref.html" />
+<meta name="assert" content="Test checks whether font-size-adjust with the ic-height metric adjusts font size.">
+<style>
+@font-face {
+  font-family: NotoSansCJK;
+  src: url(/fonts/noto/cjk/NotoSansCJKjp-Regular-subset-chws.otf);
+}
+div {
+  font-family: NotoSansCJK;
+  font-size: 100px;
+  background: green;
+  color: green;
+  writing-mode: vertical-rl;
+  text-orientation: upright;
+}
+.value {
+  /* The NotoSansCJK font has 1.0 as an aspect value for the CJK water glyph
+     (i.e., the advance height of “水” / the font size).
+     Therefore, an ic-height 2.0 means a 200% scaling up. */
+  font-size-adjust: ic-height 2.0;
+}
+.fromFont {
+  /* Likewise, ic-height from-font means 100% of the specified font size. */
+  font-size-adjust: ic-height from-font;
+}
+style>
+<div class="value">水div>
+<div class="fromFont">水div>